The taxonomic system below is modified from Brusca and Brusca (2003),
Valentine (2004), and Nielsen (2001). However, there have been major
changes in the relative positions of the phyla due to more recent molecular
phylogenetic work (summarized in Edgecombe et al. 2011). Please see the
respective phylum pages for descriptions of the higher taxa.

FIGURE 1. Reduced cladogram of the Spiralia, detail
from Figure 1, Description of the Spiralia. The topology of the cladogram is from
Edgecombe et al. (2011) and Helmkampf et al. (2008). Click on the
clades below to navigate in the hierarchical system below.